Homogeneous cerium oxide-titanium oxide composite thin film

Abstract

A simple, one-step method for producing a homogenous CeO2—TiO2 composite thin film using aerosol-assisted chemical vapor deposition (“CVD”) of a solution containing triacetatocerium (III) and tetra isopropoxytitanium (IV) on a fluorine-doped tin oxide (“FTO”) substrate at a temperature ranging from about 500 to about 650° C. Methods for using the film produced by this method.

The invention claimed is: 
     
         1 . A homogenous CeO 2 -TiO 2  composite thin film, comprising
 uniformly dispersed crystalline CeO 2  and TiO 2  phases, and   mesoporous or smooth microspheres comprising CeO 2  and/or TiO 2  having an average diameter ranging from about 0.8 to 2.0 μm,   wherein said thin film has a thickness of no more than 5 μm.   
     
     
         2 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 1  formed by a method comprising:
 dispersing a solution of metal trifluoroacetates of cerium and titanium in a carrier gas to form an aerosol mist, 
 conducting aerosol-assisted chemical vapor deposition (“AACVD”) at a temperature in a range of from 500 to 650° C. with the aerosol mist, 
 contacting the aerosol mist, in the AACVD, with a fluorine-doped tin oxide substrate, thereby depositing the homogenous CeO 2 -TiO 2  composite film onto the fluorine-doped tin oxide substrate. 
 
     
     
         3 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 2 , wherein the method of making the homogenous CeO 2 -TiO 2  composite thin film further comprises:
 reacting trifluoroacetic acid with triacetatocerium (III) and tetra isopropoxytitanium (IV) to form an initial solution of the metal trifluoroacetates;   evaporating the initial solution to obtain a residue; and   redissolving the residue in methanol to obtain the solution of metal trifluoroacetates of cerium and titanium as a methanol solution comprising the metal trifluoroacetates in a Ce:Ti molar ratio of 1.2:1 to 1:1.2.   
     
     
         4 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 3 , wherein in the method of making the homogenous CeO 2 -TiO 2  composite thin film, the reacting is conducted in methanol. 
     
     
         5 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 2 , wherein in the method of making the homogenous CeO 2 -TiO 2  composite thin film, the temperature of the AACVD and contacting are in a range of from 540 to 560° C. and wherein the thin film comprises the mesoporous microspheres having a pore size in a range of from 10 to 28 nm. 
     
     
         6 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 2 , wherein in the method of making the homogenous CeO 2 -TiO 2  composite thin film, the temperature of the AACVD and contacting are in a range of from 590 to 610° C., and wherein the thin film comprises the smooth microspheres with a substantially non-porous texture. 
     
     
         7 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 2 , wherein in the method of making the homogenous CeO 2 -TiO 2  composite thin film, the aerosol in the AACVD comprises a homogenous mixture of the metal trifluoroacetates in air, and the method comprises a single depositing. 
     
     
         8 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 7 , wherein the method of making the homogenous CeO 2 -TiO 2  composite thin film comprises no further dispersion, coating or heating. 
     
     
         9 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 1 , comprising porous heterojunctions of CeO 2 -TiO 2  which have spherical-shaped morphologies. 
     
     
         10 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 1 , having a bandgap less than either pristine CeO 2  or pristine TiO 2 . 
     
     
         11 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 1 , having a bandgap ranging from 2.5 to 2.7 eV. 
     
     
         12 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 1 , wherein the microspheres have an average diameter in a range of from 0.8 to 1.5 μm. 
     
     
         13 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 1 , wherein the microspheres have an average diameter in a range of from 0.8 to 1.0 μm. 
     
     
         14 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 1 , wherein the microspheres have an average Wadell sphericity value in a range of from 0.3 to 0.9. 
     
     
         15 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 1 , wherein the microspheres have an average Wadell sphericity value in a range of from 0.3 to 0.8. 
     
     
         16 . The homogenous CeO 2 -TiO 2  composite thin film of  claim 1 , wherein the microspheres comprise the Ce and the Ti in an atomic ratio of 0.7:1.0.